Acrylonitrile polymer composition stabilized with metal formaldehyde sulfoxylate and phenol disulfonic acid and method of making same



United States Patent i ACRYLONITRILE POLYMER COMPOSITION STA- BILIZED WITH METAL FORMALDEHYDE SULF- OXYLATE AND PHENOL DISULFONIC ACID AND METHOD OF MAKING SAME Charles H. Campbell and Lloyd T. Jenkins, Decatur, Ala assignors to The Chemstrand Corporation, Decatur, Ala, a corporation of Delaware N Drawing. Application December 17, 1956 Serial No. 628,532

17 Claims. (Cl. 26032.6)

This invention relates to the stabilization of acrylonitrile polymers and blends thereof. More particularly, it relates to the stabilization of acrylonitrile polymers and blends thereof which have a tendency to develop color upon standing or application of heat.

The term polymer, as employed in the instant decription and claims, is intended to include homopolymers, copolymers and blends thereof, said polymers containing at least 80 percent by weight of polymerized or copolymerized acrylonitrile in the polymer molecule.

Acrylonitrile polymers containing 80 percent or more of acrylonitrile are generally insoluble in the more common solvents. In those instances where suitable solvents have been found, in order to effect solution, the application of heat is usually necessary. Where heat is employed to effect solutions, from which shaped articles are to be formed, a tan to dark brown color frequently develops in the solutions and therefore is carried over into the product formed therefrom. This color also develops in solutions upon standing for prolonged periods of time.

The mechanism which causes color formation has not been definitely ascertained, although a variety of reasons therefor have been advanced. The presence of metal ions, such as iron, copper and manganese in the solutions may cause the color. The employment of amide compounds as solvents may result in formation of amines when heat is applied and cause color in the compositions. Impurities present in the solvents have also been cited as a cause. Whatever may be the reason for color formation, it results in compositions and products of undesirable standards and therefore, has been the source of concern, particu- Patented Mar. 17, 1959 ICC agent, a combined reagent comprising an organic metal sulfoxylate and phenol disulfonic acid.

Among the sulfoxylates which may be employed in practising the instant invention are those having the general formula,

)I s R 0M acetaldehyde, zinc propionaldehyde sulfoxylate, sodium propionaldehyde sulfoxylate, potassium propionaldehyde sulfoxylate, etc.

The components of the inhibiting agent may be employed in equal or unequal amounts, any one constituent being present in a range of from 99 to 1 percent in a two component system. The total amount of inhibiting agent may be employed in a range of about 0.3 to 15 percent, based on the total polymer weight. However, it is preferred that the inhibiting agent of the instant invention be present in a small amount compared to the amount of polymer dissolved. Thus, although the amount is not critical, it is preferred that the inhibiting agent be present in the amount of about 0.3 to 3.0 percent, based on the total weight of the polymer. be added to the solvents before or after the polymer is dissolved therein. The inhibiting agent permits exposure to high temperatures for prolonged standing periods without the development of the objectionable color which usually results in such solutions. The compositions of the instant invention may be prepared in a varying temperature range. For example, the compositions of the instant invention may be prepared by mixing the polymer, a suitable solvent and the inhibiting agent at any temperature or heating the mixing to a temperature up to the boiling point of the solvent.

larly in commercial operations where such types of polymers or copolymers are employed.

Accordingly, it is an object of the present invention to prevent undesirable color formation in acrylonitrile polymer compositions.

Another object is to minimize color formation when 1 solutions of the acrylonitrile polymers are permitted to mation by the presence in the solution as an inhibiting Other organic sulfonic acids which may be employed in the practice of the present invention are ortho, meta and para-phenol sulfonic acids and phenol tri-sulfonic acid, mono-sulfonated naphthols such as l-naphthol-Z- sulfonic acid, l-naphthol-3-sulfonic acid, 1-naphthol-4- sulfonic acid, l-naphthol-S-sulfonic acid, l-naphthol7- sulfonic acid, l-naphthol-B-sulfonic acid and diand trisulfonated acids of the mono-substituted naphthols named above.

Among the solvents which may be used in practising the instant invention areN,N-dimethylformamide, N,N

dimethylacetamide, aqueous zinc chloride, sulfuric acid,

aqueous nitric acid, aqueous sodium thiocyanate, ethylene carbonate, sulfolane, nitromethane, etc.

The polymeric materials, which may be employed in the practice of the present invention, are polyacrylonitrile, copolymers, including binary and ternary polymers containing at least percent by weight of acrylonitrile in the polymer molecule, or a blend comprising polyacrylonitrile or copolymers comprising acrylonitrile with from 2 to 50 percent of another polymeric material, the blend having an overall polymerized acrylonitrile content of l i at least 80 percent by weight.

polymers employed in the instant invention are those The inhibiting agent may While the preferred containing atleast 80 percent of acrylonitrile, generally recognized as the fiber-forming acrylonitrile polymers, it will be understood that the invention is likewise applicable to polymers containing less than 80 percent acrylonitrile and the same stability is realized with the inhibiting agents defined herein. The acrylonitrile polymers containing less than 80 percentacrylonitrile are" useful in forming film s, coating compositions, molding.

operations, lacquers, etc.',- in all of. which applications the'alleviation' of undesirable color is extremely important.

For example, the polymer may be a copolymer of from.

80 to 98 percent acrylonitrile and from 2 to percent of another monomer containing the r C C linkage and copolymerizable with acrylonitrile. Suitable monoolefinic monomers include" acrylic, alpha-chloroacrylic and methacrylic acids; the acrylates, such as methylmethacrylate, ethylmethacrylate, butylmethacrylate,amethoxys methyl methacrylate,beta-chloroethyl methacrylate, and. the .correspondingesters of acrylic and alpha-chloroacrylic acids; vinyl chloride, .vinyl fluoride, vinyl-bromide, vinyli-.

den'e chloride, l-chlo'ro-l-bromoethylene; methacrylonitrile; acrylamide and methacrylamide; alphachloroacr-ylamide, or monoalkyl substitution products thereof; methyl vinyl ketone; vinyl carboxylates, such as .vinyl acetate,-

vinyl chloroacetate, vinyl propionate, and. vinyl stearate; N-vinylimides, such as N-vinylphthalimide and N-vinylsuccinimide; methylene malonic esters; itaconic acid and w itaconic ester; N-vinylcarbazole;vinyl furane; alkyl vinyl esters; vinyl sulfonic acid; ethylene alpha,.beta-dicar-.-

boxylic acids or their anhydrides or derivatives, such as diethylcitraconate, diethylmesaconate, styrene, vinyl naphthalene; vinyl-substituted tertiary heterocyclic amines,

such as the vinylpyridines and alkyl-substituted vinylpyridines, for example, 2-vinylpyridine, 4-vinylpyridine,

2-methyl-5-vinyl pyridine, etc.; l-vinylimidazole and alkylsubstituted l-vinylimid'azoles, such as. 2-, 4-, or S-methyll-viny1imidazole, and other C= C containing polymerizable materials.

The polymer maybe a ternary interpolymer, for ex-v ample, products obtained by the interpolyinerization of acrylonitrile and two or more of any of the monomers,

other thanacrylonitrile, enumerated above. More specifically; and preferably, the ternary polymer comprises acrylonitrile, methacrylonitrile, and Z-Vinylpyridine. The ternary polymers preferably contain from 80 to 97 percentof' acrylonitrile, from 1 to 10 percent of a vinyl-.

pyridineor a l-vinylimidazole, and from 1 to 18 percent of another substance, 'suchas methacrylonitrile or vinyl chloride.

The polymer may also be a blend of polyacrylonitrile'v or of a binary interpolymer of from 80 to'99 percent acrylonitrilean'd from 1 to 20 percent of at least one other C"=C containingsubstance with from 2 to percent of the *weightoftheblend of a copolymer of from 10 to,

70 percent of'acrylonitrile and from 30 to 90'percent-of 98 percent acrylonitrile and from 2 to 10 percent of another mono-olefinic monomer, such as vinyl acetate, which is not 'receptive'to dyestuff, with a suffic'ient amount of a copolymer-offromdO to percent of acrylonitrile and fromw"30"to percent of a vinyl-substituted tertiary heterocyclic'amine, such' as vinylpyridine or'1-vinylimid-. azole, to give a dyeable blend having an overall vinyl substituted tertiary heterocyclic amine content of from 2 to l0'percent, based on theweight of theblend.

The polymers, useful in the'practice of the present in.-..

vention, may be prepared by any conventionalpolymeri:

zatio'nprocedures, such as mass polymerization: methods, solution polymerization methods, .orv aqueous emulsion procedures. However, the preferredpractice utilizes .sus=:.-

pension polymerization whereinrthe polymerais prepared in finelyLdiv'ided form for immediate. use inthe fiber fab-1,.

operations. The preferred suspensionpolymerize tion may utilize batch procedures, wherein monomers are charged with an aqueous medium containing the necessary catalyst and dispersing agents. A more desirable method involves the semi-continuous procedure in which the polymerization reactor containing the aqueous medium is charged with the desired monomers and the continuous withdrawal of polymer may also be employed.

The polymerization is catalyzedby means of any watersoluble peroxy compound, for example the potassium, ammonium and other water-soluble salts of peroxy acids," sodium peroxide, hydrogen peroxide, sodiumperborate; the"so'dium"salts of other'peroxy acids,--and any other water-soluble compound containing a peroxy group (-0--O-). A wide variation in the quantity of peroxy compound is possible. For example, from 0.1 to 3.0 per cent by weight of the polymerizable monomer'may be' used. The catalyst may be charged at theloutset of the reaction, or it may be added continuously or in increments throughout the reaction for the purpose of maintaining a more uniform concentration of catalyst in the reaction mass. The latter method is preferred because it tends to make the resultant polymer more uniform in its chemical and physical properties.

Although the. uniform distribution of the "reactants throughout the reaction mass can be achieved'byvigor-- ous agitation, it is generally desirable to promote-theuniform distribution of reagents .by using inert Wetting agents; or emulsionstabilizers. Suitable reagents for this pu'r-" pose are the water-soluble salts'of fatty acids, such as sodium oleate and potassium stearate, mixtures of water soluble fatty acid salts, such as common-soapsprepared by the saponificationofl animal and vegetable oils'j-the" amino soaps,- such as salts of triethanolamine and do widevariety 'of Wetting agents, which are in general'organicvcompounds containing both hydrophobic 'and' hydrophilic radicals. The quantity of emulsifying agents" will depend upon theparticular agentsselected, the ratio of monomer to be used, and the conditions'of polymeri zationn In general, however, from 0.01 to 1.0 percent'by' weight of the'monomers may be employed. I

The emulsion polymerizations are preferably conducted in glass: or glass-lined vessels which are provided with a A meansfor agitating the contents. Generally rotary stir ring devices are themost efiective means'ofinsuring the 1 intimate-contact of the reagents, but other methodsmay'" be successfully employed, for example byrockin'g or tum bling the reactors; The polymerization equipment g'en erally'used is conventional in the art and the adaptation of a particular. typeof apparatus to the reaction 'CODtCm-"i plated is within the province of one skilled in the art? The articles manufactured: therefrom may be produced by well-known conventional methods, for'example the wet-spinning, dry-spinning and melt-spinning methods'fo'r'; producing fibers.

The following examples :are illustrative rather than-' limitative and all parts, proportions and percentagesare by weight unless otherwise specified.

EXAMPLE I 7.5 grams of a polymer blend of 88 percent of a polyinercontaining 94 percent of acrylonitrile and 6 percentof'vinylacetate and 12 percent of a copolymer of 5.0 percentof acrylonitrile and 50 percent of 2-methyl-5-' vinyl pyridine were added to milliliters 'of 'N,N-di'-"* methylacetamidex containing approximately -0.05 gram ofv titanium dioxide. The mixture was stirred and heated'to' 70 C.. It was then quickly cooled .to room temperatures and theicolorrmeasuredv This samplewasxused asaa con-,2 trol. .The purity is set forth below. Subsequently,' =a like? sample: rwasieprepared but with 0.150 gramiof: a color-sin hibitor containing 0.075 gram each of zinc formaldehyde g suifoxylate and phenol disulfonic acid. The purity isset forth below. 1 7

Table l Inhibitor Percentage Purity I a Used l r EXAMPLE II 7.5 grams of a copolymer containing 94 percent of acrylonitrile and 6 percent of vinyl acetate were added to. 45 milliliters of N,N-dimethylacetamide containing approximately 0.05 gram of titanium dioxide. The mixture was stirredand heated for 35 min'utesat 70 C. I

It wasthen quickly cooled to room temperature and the colormeasured. This sample was used asa control. The purity is set forth below. Subsequently, alike sampic was prepared but with 0.150 gram of a color inhibitor containing 0.075 gram each of zinc formaldehyde ,sulf

oxylate and. phenol disulfonic acid. The purityis set. forth below. H

Table II 3 Percentage Purity Used I U EXAMPLE m zincforrnaldehyde sulfoxylate and phenol disnlfonic acid.

The purity is set forth below.

Table III namesl Percentage Puri y Used Contr l 10.8' Zinc Formaldehyde Sulioxylate and Phenol Dlsulfonlc Acid 2 2. 7

The tests for color indicative of approaching whiteness used throughout the examples consist of measurements purity as calculated from the tristimulus values determined on a General Electric Spectrophotometer by the methods recommended by the Standard Observer and Coordinate System of the International Commisson on Illumination, as fully set forth in the Handbook of Colorimetry published by The Technology Press, Massachusetts Institute of Technology in 1936.

The compositions of the instant invention present many advantages. For example, products formed from the polymer solutions of the instant invention are free of objectionable color and therefore of greater commercial value. In preparing the polymer solutions, heat may be applied without the danger of color formation and the solutions, if necessary, may stand for prolonged periods and remain free of color. The inhibiting agents are readily available and inexpensive. Therefore, no great increase in production cost is necessary. The compositions containing the inhibitors may be prepared without going through detailed and elaborate procedures that 2, and M is a metal selected from the group consisting necessitate expensive changes in the design of the ap: paratus used to manufacture them. c

c It will be understood to those skilled in the art that, many apparentlywidely different embodiments of this. invention can be made without departing from the spirit and scope thereof. Accordingly, it is to be understood that this invention is not to be limited to the specific embodiments thereof except as defined in the appended claims.

We claim: i

1. A new composition of matter comprising a. polymer containing at least percent of polymerized acrylo nitrile and up to 20percent of another .polymerizablemono-olefinic monomer copolymerizable therewith, a solvent therefor, and an inhibiting agent containing substanthe general formula,

a I R 0. .1 wherein R isan alkanol group containing 1 to 3 carbon atoms and having the free valence on a carbon atom joined to the hydroxy group, n is an integer from 1 to of sodium, potassium and zinc; and phenol disulfonic acid. a

2. A new composition of matter as defined in claim 1 wherein the polymer is a copolymer containing from 80 "to 98 percent of acrylonitrile and from 2 to 20 percent of another polymerizable mono-olefinic monomer copolymerizable therewith.

3. A new composition of matter as defined in claim 1 wherein the polymer is, a blend of 80 to 99 percent of (A) a copolymercontaining to 98 percent of acryloof acrylonitrile and 30 to 90 percent of 2-methyl-5-vinyl pyridine.

4. A new composition of matter as defined in claim 1 wherein the polymer. is polyacrylonitrile.

5. A new composition of matter as defined in claim 1 wherein the compound is sodium formaldehyde sulfoxylate.

6. A new composition of matter as defined in claim 1 wherein the compound is potassium formaldehyde sulfoxylate.

7. A new composition of matter as defined in claim 1 wherein the compound is zinc formaldehyde sulfoxylate.

8. A new composition of matter as definedin claim 1 wherein. the solvent is N,N-dimethylaceta-mide.

9. A newpcomposition of matter comprising a poly formula,

wherein R is an alkanol group containing 1 to 3 carbon atoms and having the free valence on a carbon atom joined to the hydroxy group, n is an integer from 1 to 2, and M is a metal selected from the group consisting of sodium, potassium and zinc; and phenol disulfonio acid. 10. A new composition of matter comprising a copoly- R OJ" wherein R'is an alkanol group containing 1 to '3 carbon atoms-and having the free valence on a carbon atom joined to the hydroxy group, n is an integer from Ito 2, and M is a metal selected from the group consisting of sodium, potassium and zinc; and phenol disulfonic acid.

11. A new composition of matter comprising a polymer blend of 80 to 99 percent of (A) a copolymer containing 90 to 98 percent of acrylonitrile and 2 to percent of vinyl acetate and 1 to 20 percent of (B) a copolymer containing 10 to'70 percent of acrylonitrile and 30 to 90 percent of Z-methyl-S-vinylpyridine, a solvent therefor, and 0.3 to percent, based on the total Weight Of the polymer, of an inhibiting agent, said inhibiting,

agent containing substantially equal proportions" by weight of'a compound having the general formula,

' sodium, potassium and zinc; and phenol disulfonict acid;

13. A method for preparing a new composition of matter comprising mixing a polymer containingatleastfifl.

percent of polymerized acrylonitrile and ,up to percent of another polymerizable mono-olefinic monomer copolymerizable'therewith, a solvent therefonand an inhibiting agent containing substantially equal proportions by weight of a compound having the general formula,

sodium, potassium and zinc; and phenol disulfoniciacid,

l. and heating the mixture to form a homogeneousisolution.

14? The method as defined in claim 13 whereinthe polymer is aicopolymer containing from 80 to98percent of-acrylonitrile and from 2 to 20 percent of, another,

polymerizable mono-olefinic monomer copolymerizable therewith.

wherein R' is an alkanol group containing 1. to 3 carbon f atoms and having the free valenceon a carbon atom joined to the hydroXy group, n is an integer from 1,:to,2,

wherein R is an .alkanol group containing 1 to 3'carbon' atoms and having the free valence on a carbon atom joined to the hydroxy group, n is an integer from 1 to 2,

and M is a metal selected from, the group consisting of polymer is 'a blend of to 99 percent of (A) a copolymer' containing m 98 percent of acrylonitrile and 2 to 10 percent! of vinyl acetate and 1 to20 percent of (B) a rcopolymer containing 10 to 70 percent of acrylonitrile' ,.H30'

and 30 to I90 percent-of Z-methyl-S-vinyl pyridine.

1-6. The: method as defined in claim 13 wherein the polymer is polyacrylonitrile.

17. A method for preparing anew composition of Aamatterco mprising mixing apolymer blendnof'80cto .99

percent of (A) a copolymer containing 90- to '98v-percent of acrylonitriletand 2 to 10 percent of vinyl acetateand i 1 to'2t) percent of (B) a copolymer containing 10to :70 percent.ofacrylonitrile and 30 to v9O percent oil-methyl- 5-vinyl pyridine, a solvent therefor, and 0.3 to 15 per- CCIIL baSEd on. the total weight of. the polymer; of aninhibiting agent, said inhibiting agent containing substan tiallyrequal proportions by weight 7 of zinc formaldehyde sulfoxylate and phenol disulfonicacid, and heating-the mixture to a temperature in a range of 25" C.-to:ithe' boiling point of said mixture to solution.

. References Cited in the file of this patent UNITED STATES PATENTS form a homogeneous FOREIGN rATENTs 1,027,445 France May '12, 1953 15. The method as defined in claim 13 wherein the Stanin et a1. June 16, I 

1. A NEW COMPOSITION OF MATTER COMPRISING A POLYMER CONTAINING AT LEAST 80 PERCENT OF POLYMERIZED ACRYLONITRILE AND UP TO 20 PERCENT OF ANOTHER POLYMERIZABLE MONO-OLEFINIC MONOMER COPOLYMERIZABLE THEREWITH, A SOLVENT THEREFOR, AND AN INHIBITING AGENT CONTAIN ING SUBSTANTIALLY EQUAL PROPORTIONS BY WEIGHT OF A COMPOUND HAVING THE GENERAL FORMULA, 